A vehicle traveling through an environmental media such as air experiences drag. The drag is actively modulated by energy beams which may either increase or decrease the drag. The energy beams may provide either a chemical, acoustic or electromagnetic energy at a transition region between turbulent and laminar flows or at the leading edge of a laminar flow or in the direction of a crosswind in order to facilitate the respective increase or decrease in drag. Where the energy beams are acoustic or ultrasonic, some or all of the beams may be used to generate an audible signal, in a directional manner, outside the vehicle.